Since KeyMaster goes to the first patch of the
first song whenever you open a document, you might want to fill that
patch with commands that initialize your MIDI setup. For example,
in the enter message of the first patch, you could:

You can use KeyMaster to play some notes for
you. Use MIDI commands in a patch's enter message to play a note (note
on, value, velocity) then use MIDI commands in the exit message to
release the note.

A MIDI note on or off message consists of two parts, note number
and velocity. Notes range from 0 to 127; middle C is note number
60 (hex 0x3C). Velocity range is 0 - 127, where 0 is the same
as note off.

A note is not turned off until either a note off command is sent
or (on most synths) an all-notes-off command is sent.

You can also enter note commands into a programmable MIDI message
and send the message from a song or by hand.

You might want to set up a song that helps you tune your instruments
by sending the proper program changes and entering note on and note
off commands that play the tuning note on different synths. (Yes,
you actually had to tune most older synths.) For example,

Patch One

Enter message: program changes and note-ons for reference synth
A and another synth (B).

Exit message: note-off for synth B.

Patch Two

Enter message: program change and note-on for synth C.

Exit message: note-off for synth C.

Patch Three

Programmable MIDI messages can be used for a number of things.
For example, you can have one message for each of the "start" (250,
hex 0xFA), "continue" (251, hex 0xFB), and
"stop" (252, hex 0xFC) MIDI commands to control your
sequencer or drum machine. This turns your computer keyboard into
a MIDI control panel.

You might want to have a message that resets all of your synths
to full volume.

See your MIDI devices' manuals for the specific MIDI commands
to which each responds.